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[PATCH 3.14 06/25] skbuff: Fix skb checksum partial check.

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3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pravin B Shelar <pshelar@nicira.com>

[ Upstream commit 31b33dfb0a144469dd805514c9e63f4993729a48 ]

Earlier patch 6ae459bda tried to detect void ckecksum partial
skb by comparing pull length to checksum offset. But it does
not work for all cases since checksum-offset depends on
updates to skb->data.

Following patch fixes it by validating checksum start offset
after skb-data pointer is updated. Negative value of checksum
offset start means there is no need to checksum.

Fixes: 6ae459bda ("skbuff: Fix skb checksum flag on skb pull")
Reported-by: Andrew Vagin <avagin@odin.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/skbuff.h |    2 +-
 net/core/skbuff.c      |    9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2348,7 +2348,7 @@ static inline void skb_postpull_rcsum(st
 	if (skb->ip_summed == CHECKSUM_COMPLETE)
 		skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
 	else if (skb->ip_summed == CHECKSUM_PARTIAL &&
-		 skb_checksum_start_offset(skb) <= len)
+		 skb_checksum_start_offset(skb) < 0)
 		skb->ip_summed = CHECKSUM_NONE;
 }
 
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2862,11 +2862,12 @@ EXPORT_SYMBOL(skb_append_datato_frags);
  */
 unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
 {
+	unsigned char *data = skb->data;
+
 	BUG_ON(len > skb->len);
-	skb->len -= len;
-	BUG_ON(skb->len < skb->data_len);
-	skb_postpull_rcsum(skb, skb->data, len);
-	return skb->data += len;
+	__skb_pull(skb, len);
+	skb_postpull_rcsum(skb, data, len);
+	return skb->data;
 }
 EXPORT_SYMBOL_GPL(skb_pull_rcsum);
 


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[PATCH 3.14 00/25] 3.14.56-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 02/25] af_unix: Convert the unix_sk macro to an inline function for type safety Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 24/25] sched/preempt: Rename PREEMPT_CHECK_OFFSET to PREEMPT_DISABLE_OFFSET Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 14/25] btrfs: fix use after free iterating extrefs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 06/25] skbuff: Fix skb checksum partial check. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 15/25] arm64: errata: use KBUILD_CFLAGS_MODULE for erratum #843419 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 16/25] i2c: rcar: enable RuntimePM before registering to the core Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 25/25] sched/preempt: Fix cond_resched_lock() and cond_resched_softirq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 05/25] skbuff: Fix skb checksum flag on skb pull Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 09/25] ethtool: Use kcalloc instead of kmalloc for ethtool_get_strings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  Re: [PATCH 3.14 00/25] 3.14.56-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-10-23 23:10 +0200
  Re: [PATCH 3.14 00/25] 3.14.56-stable review Guenter Roeck <linux@roeck-us.net> - 2015-10-24 04:10 +0200

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